This invention relates to a high speed thermal spray coating method comprising the steps of producing a high speed flame from a combustion gas and spraying a thermal spray coating material powder using the high speed flame onto the surface of a base material to be thermal spray coated, thus forming a coating on the surface of the base material. In particular this method is also suitable for forming a coating with improved lubricity and abrasion resistance on a part of the surface or the entire surface of a swash plate for an air compressor pump manufactured of aluminum alloy, cast iron or steel based alloy.
The swash plate of an air compressor pump, for example, is structured in such a manner that the swash plate rotates to reciprocally move a piston through shoes which are in contact with the circumferential part of both surfaces of the swash plate, and therefore the shoes slidingly move over the peripheral surfaces of the swash plate.
The swash plate is ordinarily made of aluminum alloy, cast iron or steel based alloy, whereas the sliding shoes of mating parts are formed of SUJ2 (Japanese Industrial Standards). When lubrication becomes insufficient, seizure is apt to occur. Therefore, a Sn plating or Teflon (tetrafluoroethylene resin) coating is provided on the surfaces of the swash plate, and in addition, a treatment such as a coating of MoS.sub.2 (lubricant) is applied thereon.
However, in the case where the Sn-plated swash plate reaches a non-lubricant state and yet is placed under an operating condition in which the swash plate rotates with a high speed and bears a high load, the abrasion loss on the surface of the swash plate increases, eventually ending in seizure taking place between the swash plate and the shoe. Also, the Sn plating takes about 30 minutes to form a plated layer 10 .mu.m thick. Portions of the swash plate not requiring the plating need to be masked. A lot of time is required for the coating and removing of the masking material and, as such, the Sn coating process has an inferior workability.
Similarly, when the Teflon-coated swash plate is in a non-lubricant state and is placed under an operating condition requiring a high speed rotation and a high load receiving, the abrasion loss on the swash plate surface increases. It is also necessary when performing the Teflon coating to mask the portions of the swash plate surface not requiring the coating, which takes a substantial length of time, thus making it a rather troublesome work.
At present, as far as the inventors know, there is no coating material suitable for a swash plate made of, for example, aluminum alloy, cast iron or steel based alloy, which relative to shoes made of SUJ2, exhibits satisfactory abrasion resistance, scuff resistance, seizure resistance and pressure resistance under the conditions of a high speed rotation, high load and no lubrication.
Further, there is no method for improving surface properties which is capable of easily masking portions not required to have a coating using the wet process, as well as quickly removing the mask after forming the coating and also forming the coating at a high speed.